The present invention generally relates to rotary recording medium reproducing apparatuses capable of performing special reproduction, and more particularly to a rotary recording medium reproducing apparatus in which a reproducing element is shifted to an adjacent track in a state where tracking servo is constantly and stably performed upon special reproduction.
A new information signal recording and/or reproducing system has been proposed in a U.S. Patent Application Ser. No. 785,095 entitled "Information Signal Recording System" filed Apr. 6, 1977, now U.S. Pat. No. 4,331,976, of which the assignee is the same as that of the present application. According to this proposed system, the recording system forms pits in accordance with the information signal being recorded along a spiral track on a flat disc-shaped recording medium (hereinafter referred to as a disc), without forming a groove therein. In this reproducing system, a reproducing stylus traces over along this track thereby to reproduce the recorded information signal in response to variations in the electrostatic capacitance.
In this system, since no grooves for guiding the reproducing stylus are provided on the disc, it becomes necessary to record pilot or reference signals on or in the vicinity of a track of the information signal such as a video signal, on the disc. Upon reproduction, the reference signals are reproduced together with the video signal. Tracking control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
By the use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged since the recording track has no groove. The reproducing stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow-motion, or quick-motion reproduction becomes possible.
Thus, in a U.S. patent application Ser. No. 4,813 entitled "Special Reproducing System in an Apparatus for Reproducing Video Signals from a Rotary Recording Medium" filed Jan. 19, 1979, now U.S. Pat. No. 4,340,907, of which the assignee is the same as that of the present application, a special reproducing system in a disc reproducing apparatus was proposed which is capable of performing a special reproduction in which a picture having a motion different from that upon normal reproduction is obtained in an excellent manner.
The special reproducing system comprises a reproducing element for tracing the track of the disc and picking up the recorded signal, a tracking control mechanism for operating in response to kick pulses applied thereto to cause the reproducing element to shift to an adjacent track turn of the spiral track, and a kick pulse generating circuit for generating kick pulses with timings corresponding to the vertical blanking period positions of the recorded video signal, where the kick pulses are of a number corresponding to the number of operational modes for carrying out a special reproduction differing from normal reproduction at every revolution period of the disc, and supplying the kick pulses to the tracking control mechanism. The reproducing element is shifted to an adjacent track turn within the vertical blanking period of the recorded video signal, by the tracking control mechanism responsive to the kick pulses.
Accordingly, the noise introduced when the reproducing element moves to an adjacent track does not appear in the picture, and a special reproduction such as still reproduction, slow-motion and quick-motion reproduction in the forward direction, and normal-speed, slow-motion, and quick-motion reproduction in the backward direction can be performed in which a fine picture is obtained.
In the above previously proposed system, the kick pulses are generated during the interval of the vertical synchronizing signal within the vertical blanking period of the recorded video signal. However, first and second reference signals for tracking control are not recorded within the interval of the vertical synchronizing signal, and only a third reference signal for switching is recorded. Accordingly, tracking control is not performed during the interval of the above vertical synchronizing signal. Generally, since the interval of the vertical synchronizing signal is a short interval in the range of three horizontal scanning periods (3H), even when the tracking control is not performed during this interval, no inconveniences are introduced upon a normal reproduction mode.
However, when the reproducing stylus is forcibly shifted to an adjacent track during the interval of the vertical synchronizing signal when the tracking control is not performed, upon a special reproduction mode, disturbance is introduced in the tracking control operation. Hence, there was a disadvantage in that the tracking control operation became unstable.
Furthermore, in the above disc, the sides on which the first and second reference signals are recorded with respect to the main track changes for each track turn. Hence, when the position where the reproducing stylus is to be shifted is a position where the third reference signal is recorded, it became necessary not to generate the switching signal. On the other hand, when the position where the reproducing stylus is to be shifted is a position where the third reference signal is not recorded, it became necessary to generate the switching signal. Accordingly, the construction of a switching signal generating circuit became complex. Moreover, in a case where the generation of the switching signal is performed by use of a micro-computer, there was a disadvantage in that the program for generating the switching signal became complex.